Numerous RF-based repeaters exist that provide wireless communication network coverage to areas in which such coverage would otherwise be weak or non-existent. Such coverage is important because a high percentage, which some studies indicate to be near 40%, of network subscribers live, work or travel in areas having such weak or non-existent coverage.
Several types of RF-based repeaters support frequency division duplexing (FDD) systems and enhance network coverage in networks providing wireless service in various frequency bands and supporting various wireless standards, including IS-95, IS-2000, W-CDMA, HSDPA/HSUPA, TDS-CDMA, IEEE802.11, IEEE802.16, and the like. In such a configuration, a first repeater unit in communication with a wireless base station (BS) receives RF signals through an antenna, typically located at the top of a large structure such as a shopping mall or parking deck. The first repeater unit then communicates the downlink RF signals, often along with a local oscillator (LO) signal, to a remotely located second repeater or repeaters over existing or new building cabling. Some of these types of repeater systems transport the RF signals at their original frequencies, while others utilize an intermediate frequency (IF) for transporting the signals. Where an intermediate frequency is used, an LO reference signal is provided along with the IF based signal. These repeater systems are often referred to an “in-building distribution systems.” The second repeaters, often referred to as remote or slave units, in turn communicate with subscriber terminals to provide wireless coverage within the structure and communicate subscriber terminal RF signals back to the transceiver through an uplink established with the first repeater unit through the new building cabling, including in some cases fiber optic cabling. The LO signal enables the first repeater unit in communication with the BS and the second repeaters in communication with subscriber terminals to minimize frequency offset.
However, the above repeater typically is complex, and therefore expensive, to install and involves a significant amount of network planning due to the size of the structures in which it is typically implemented. Generally, new cabling must be used for these systems, and in most deployments a single cable must be installed between the first repeater or master unit and each remote unit. The replication of cabling drives the cost of the deployment due to both materials and labor. Because a cable is installed from the master to each remote, rearranging the remote units or installing additional remote units is difficult and expensive. Finally these remote units are generally not in communication with the master unit and therefore if malfunctions arise, the operator will often remain unaware of the condition for an indefinite period of time.
Another RF-based repeater that has increased in popularity in countries such as South Korea finds use in residential applications. In such a system, typically cabling is run from an external antenna outside to an indoor repeater unit that transmits on a second antenna within the home. Performance of such a system is dependent upon the isolation of the two antennas, and can vary based on their physical separation, and antenna orientation. Further, the benefits of this solution are typically outweighed by the costs for requisite professional installation.
While such a configuration does not need to tap into existing home wiring or cabling, professional installation is required as previously noted because the repeater includes a transmit antenna and a receive antenna that must be physically separated. Also, the signal strength of the repeater must be adjusted downwardly in proportion to the proximity of the transmit and receive antennas to one another to prevent transmit and receive signals, which share the same frequency, from oscillating due to their coupling. As a result of the signal strength of each repeater being adjusted downwardly, such a repeater provides incremental improvement in network coverage and signal strength in many cases, thereby resulting in only marginal benefit to some network subscribers, and a highly variable outcome for the carriers who often install them.
One known same-frequency RF-based residential repeater in a self-install package is available in which isolation between the transmit and receive antennas in each repeater is achieved by using directional antennas, by physically separating the antennas and by adjusting the repeater transmit/receive signal strength downwardly to prevent receiver desensitization and oscillation. However, the repeaters themselves are large and bulky due to the need to physically separate the antennas and are expensive due to their many RF components. The benefit provided by such repeaters is marginal due to the close proximity of both antennas, and therefore the minimal isolation limits their effectiveness. In addition, the solution provides incremental improvement in network coverage and signal strength, thereby resulting in only marginal benefit to network subscribers.